This invention relates to a method for preparing an improved hydrotreating catalyst containing molybdenum and/or tungsten, particularly with respect to hydrodenitrification (HDN) activity.
Considerable research has been undertaken to develop and commercialize new, cost effective hydrotreating catalysts for large volume first stage hydrocracking and catalytic cracking feed hydrotreater applications. The inclusion of significant amounts of 1000.degree. F..sup.+ residual components, including cracked stocks, in the feed to these processes has created severe activity and stability problems for the catalysts currently used commercially in these applications. The growing demand for new catalysts for up-grading such poor quality feedstocks has led to the discovery of an improved catalyst by oxidizing zero-valence molybdenum and/or tungsten with elemental sulfur (S.sub.8) to yield a metal sulfide directly instead of by first oxidizing the metals (e.g., by calcining in air) and then sulfiding them.
It is known to combine molybdenum carbonyls with alumina to prepare a catalyst for the metathesis of olefins (J. Mol. Catalysis, 1 (1975/76)77-84. We have discovered that molybdenum and/or tungsten carbonyls can be directly oxidized to the corresponding sulfide with free sulfur to achieve hydrotreating catalysts with greatly enhanced hydrodenitrification activity.